CA3141786A1

CA3141786A1 - Secondary battery inspection method and secondary battery inspection device

Info

Publication number: CA3141786A1
Application number: CA3141786A
Authority: CA
Inventors: Ichiro Munakata; Satoshi Tanno; Hideki Shoji
Original assignee: Toyo System Co Ltd
Current assignee: Toyo System Co Ltd
Priority date: 2020-04-13
Filing date: 2021-03-19
Publication date: 2021-10-21
Anticipated expiration: 2041-03-19
Also published as: US20230034016A1; KR20210149795A; EP3951409A4; CA3141786C; TWI774291B; JP2021167798A; CN113826020B; TW202201019A; WO2021210346A1; EP3951409A1; CN113826020A; JP6997473B2

Abstract

Provided is a secondary cell inspection device with which it is possible to improve inspection accuracy of a secondary cell while also simplifying the inspection thereof. A model parameter value of a secondary cell model is identified on the basis of a sampling rate T. The secondary cell model expresses internal resistance impedance for a secondary cell 200 using an IIR transfer function and a FIR transfer function. A model output voltage is estimated as a mode of voltage variation outputted from an assignment model when an impulse current (t) is inputted to said assignment model, which is the secondary cell model in which the model parameter value is identified. On the basis of a voltage measurement result for the secondary cell 200 when the impulse current I(t) flows through said secondary cell 200, and on the basis of the assignment model output voltage, the performance of the secondary cell 200 based on the sampling rate T is assessed.

Description

DESCRIPTION
Title of the Invention SECONDARY BATTERY INSPECTION METHOD AND SECONDARY
BATTERY INSPECTION DEVICE
Technical Field [0001] The present invention relates to a technique for inspecting a secondary battery such as a lithium-ion battery.
Background Art

[0002] As a method of inspecting the internal state of a secondary battery, an AC
impedance analysis method based on a frequency response analysis (FRA) method is well known, and a method of applying an equivalent circuit model to decompose the secondary battery into time-constant elements in order to interpret various internal reactions of the secondary battery is established.
Citation List Patent Literature

[0003] Patent Literature 1: Japanese Patent No. 5924617 Summary of Invention Technical Problem

[0004] However, multipoint measurements from a high frequency range of about kHz up to a low frequency range of about 10 mHz to 100 mHz are required for the AC
impedance analysis. Therefore, the inspection of the secondary battery takes a long time.
Further, since a dedicated measuring device is required, it is difficult to put the method into practical use in such a scene that a short takt time is prerequisite such as a mass production line. Although an inspection machine having a certain degree of accuracy in a short time is required upon mass production shipment inspection of secondary batteries and product acceptance inspection, since the characteristics of each battery is changing depending on the operating state of the battery (such as voltage (SOC), operating current, and battery temperature), inspection must be performed by setting constant conditions.
Therefore, an inspection device with good reproducibility is desired. Although pass/fail Date recue /Date received 2021-11-24 determination criteria are set from a statistical population distribution in the mass production line or the like, such settings are possible only when the inspection conditions are fixed, and there were hardly any methods of being able to determine pass/fail of a secondary battery on the market.

[0005] Therefore, the object of the present invention is to provide a secondary battery inspection device or the like capable of improving inspection accuracy while simplifying the inspection of a secondary battery.
Solution to Problem

[0006] A secondary battery inspection device according to the present invention includes:
a voltage recognition element which recognizes a measurement result of voltage of a secondary battery when an impulse current flows into the secondary battery;
a model parameter setting element which identifies, based on a sampling period, a value of a model parameter of a secondary battery model in which impedance of internal resistance of the secondary battery is expressed by transfer functions respectively representing an IIR system and an FIR system;
a voltage estimation element which, when the impulse current is input to a specified model as the secondary battery model the value of the model parameter of which is identified by the model parameter setting element, estimates a model output voltage as a voltage change form output from the specified model; and an evaluation element which evaluates the performance of the secondary battery according to the sampling period based on the measurement result of the voltage of the secondary battery recognized by the voltage recognition element, and the specified model output voltage estimated by the voltage estimation element.

[0007] It is preferred that the model parameter setting element individually identifies the value of the model parameter based on each of a plurality of sampling periods, respectively, the voltage estimation element estimates a plurality of model output voltages as voltage change forms respectively output from a plurality of specified models when the impulse current is input to the plurality of specified models as individual Date recue /Date received 2021-11-24 secondary battery models with the values of the model parameter identified by the model parameter setting element, and the evaluation element evaluates a plurality of performances of the secondary battery respectively according to respective of the plurality of sampling periods based on the measurement result of the voltage of the secondary battery recognized by the voltage recognition element, and respective of the plurality of specified model output voltages estimated by the voltage estimation element.

[0008] It is also preferred that the secondary battery inspection device further includes a temperature compensation element which recognizes a measurement result of temperature of the secondary battery, wherein the model parameter setting element corrects the value of the model parameter based on the measurement result of the temperature of the secondary battery recognized by the temperature compensation element.
Brief Description of Drawings

[0009] FIG. 1 is an explanatory diagram related to the configuration of a secondary battery inspection device as one embodiment of the present invention.
FIG. 2A is a first illustrated diagram of an equivalent circuit of the internal resistance of a secondary battery.
FIG. 2B is a second illustrated diagram of the equivalent circuit of the internal resistance of the secondary battery.
FIG. 2C is a third illustrated diagram of the equivalent circuit of the internal resistance of the secondary battery.
FIG. 2D is a fourth illustrated diagram of the equivalent circuit of the internal resistance of the secondary battery.
FIG. 3A is a diagram representing a transfer function of a connection resistance component Ro of the secondary battery.
Date recue /Date received 2021-11-24 FIG. 3B is a diagram representing an IIR transfer function of the i-th RC
parallel circuit composed of a charge transfer resistance Ri and a capacitor C.
FIG. 3C is a diagram representing an IIR transfer function of an inductance component L.
FIG. 3D is a diagram representing an FIR transfer function of a Warburg impedance Wo.
FIG. 4 is an explanatory chart related to Nyquist plots of the secondary battery.
FIG. 5A is an explanatory chart related to a first evaluation index according to a first sampling period.
FIG. 5B is an explanatory chart related to a second evaluation index according to the first sampling period.
FIG. 5C is an explanatory chart related to a third evaluation index according to a second sampling period.
Description of Embodiment

[0010] (Configuration of Secondary Battery Inspection Device) A secondary battery inspection device 100 as one embodiment of the present invention illustrated in FIG. 1 is composed of a processor (arithmetic processing unit), a memory (storage device), an I/O circuit, and the like. In the memory or a storage device separate from this memory, a program (software) is stored and held in addition to various data such as parameters for defining a secondary battery model. For example, each of plural identifiers for identifying a secondary battery or the type of a target machine element (identified by the standard and specifications) in which this secondary battery is installed, and each of plural secondary battery models are stored and held in the memory in association with each other. The processor reads necessary program and data from the memory, and executes arithmetic processing according to the program based on the data to execute arithmetic processing or a task to be described later.
Date recue /Date received 2021-11-24

[0011] The secondary battery inspection device 100 includes an OCV detection element 102, a subtraction element 104, a temperature compensation element 110, a first sampling period output element 111, a first model parameter setting element 112, a first voltage estimation element 114, a first division element 116, a second sampling period output element 121, a second model parameter setting element 122, a second voltage estimation element 124, a second division element 126, a first evaluation element 142, a second evaluation element 144, and a third evaluation element 146.

[0012] (Secondary Battery Model) Each of the secondary battery models is a model representing voltage V(t) output from a secondary battery 200 when current I(t) is input to the secondary battery 200. The voltage V(t) is defined by equation (01) using an open circuit voltage OCV of the secondary battery 200 and a transfer function H(t) of the internal resistance.

[0013] V(t) = OCV + H(t)1(t) ...(01)

[0014] The transfer function H(t) of an equivalent circuit model of the internal resistance of the secondary battery is defined by equation (02).

[0015] [Math. 11 H(t) = Ho(t) + E1711 H1(t) + Hw(t) + HL(t) ... (02)

[0016] "Ho(t)," "Hi(t)," "Hw(t)," and "HL(t)" are defined by parameters representing the characteristics of the internal resistance of the secondary battery.

[0017] In FIG. 2A, an example of an equivalent circuit of the internal resistance of the secondary battery 200 is illustrated. In this example, the equivalent circuit of the internal resistance is defined by a series circuit of a connection resistance component Ro, the i-th RC parallel circuit (i = 1, 2, ..., m) composed of charge transfer resistances Ri and capacitors C, a Warburg impedance Wo, and a coil L. In FIG. 2A, the number, m, of RC
parallel circuits connected in series is "4." As illustrated in FIG. 2B, the number, m, of RC
parallel circuits connected in series may be smaller than 4, or may be larger than 4. As illustrated in FIG. 2C and FIG. 2D, respectively, the Warburg impedance Wo may also be connected in series with a resistance R in at least any one of RC parallel circuits (for Date recue /Date received 2021-11-24 example, in the first RC parallel circuit). Further, each capacitor C may be replaced with a CPE (Constant Phase Element). In addition, the coil L may be omitted.

[0018] The transfer function Ho(z) of the resistance Ro is defined by equation (10). In FIG. 3A, a block diagram representing the transfer function Ho(z) of the resistance Ro is illustrated.

[0019] Ho (z) = Ro ... (10)

[0020] The dependency of Ro on temperature 0 is predetermined according to the equation (10) based on the measurement results of Nyquist plots of a reference secondary battery at different temperatures 0 (see FIG. 4), respectively. In other words, the coefficient Ro is defined as a dependent variable or a function when the temperature 0 for defining the transfer function Ho(z) of the resistance Ro is taken as the main variable.

[0021] The transfer function Hi(z) of the i-th RC parallel circuit is defined by equation (20) as an IIR (Infinite Impulse Response) system. In FIG. 3B, a block diagram representing the transfer function Hi(z) of the i-th RC parallel circuit is illustrated.

[0022] Hi(z) = (bo + biz-1)/(1 + aiz-1) ...(20)

[0023] A transfer function Hi(s) of the i-th RC parallel circuit in an s region is expressed by equation (21).

[0024] Hi(s) = Ri/(1 + tis) (where ri = 1/RC) ...(21)

[0025] When the transfer function Hi(s) is bilinear-transformed (s ¨> (2/T)(1-z-1)/(1 +
z-1) (where T is a sampling period)), the transfer function Hi(z) of the i-th RC parallel circuit in a z region is expressed by equation (22).

[0026] Hi(z) = {Ri/(1 + 2'r/T) + Ri/(1 + 2-ri/T)z-11 /{1+(1 - 2ti/T)/(1 + 2-ri/T)z-11 ... (22)

[0027] From a comparison between the equations (20) and (22), each of coefficients bo, b, and ai in the IIR transfer function is defined by each of equations (221) to (223), respectively.

[0028] bo = Ri/(1 + 2'r/T) ...(221)

[0029] bi = Ri/(1 + airr) ... (222)

[0030] ai = - { 1+(1 - 2'r/T)/(l + 2'r/T)} .. (223) Date recue /Date received 2021-11-24

[0031] The dependencies of Ri and Ci on temperature 0 are predetermined according to the equation (21) based on the measurement results of Nyquist plots of the secondary battery at different temperatures 0 (see FIG. 4), respectively. In other words, each of the coefficients bo, b, and ai that define the transfer function Hi(z) of the i-th RC parallel circuit is defined as a dependent variable or a multivariable function when the temperature 0 and sampling frequency T are taken as main variables.

[0032] The transfer function HL(z) of the coil L is defined by equation (30) as the transfer function of the IIR system. In FIG. 3C, a block diagram representing the transfer function HL(z) of the coil L is illustrated.

[0033] HL(z) = (2L0/T)(1 - z-1)/(1 + z-1) ...(30)

[0034] A transfer function HL(s) of the coil L in the s region is expressed by equation (31).

[0035] HL(s) = sLo ...(31)

[0036] When the transfer function HL(s) is bilinear-transformed, the transfer function HL(z) of the coil L in the z region is represented by equation (32).

[0037] HL(z) = {2Lo/T-2Lo/Tz-1}/(1 + z-1) ...(32)

[0038] From a comparison between the equations (30) and (32), each of the coefficients bo, b, and ai in the IIR transfer function is defined by each of equations (321) to (323), respectively.

[0039] bo = 2L0/T ... (321)

[0040] bi = -2L0/T ...(322)

[0041] a=-1 ...(323)

[0042] The dependence of Lo on temperature 0 is predetermined according to the equation (31) based on the measurement results of Nyquist plots of the reference secondary battery at each of different temperatures 0 (see FIG. 4), respectively. In other words, each of the coefficients bo and bi that define the transfer function Hi(z) of the coil Date recue /Date received 2021-11-24 L is defined as a dependent variable or a multivariable function when the temperature 0 and sampling frequency T are taken as main variables.

[0043] The transfer function Hw(z) of the Warburg impedance Wo is defined by equation (40) as a transfer function of a FIR (Finite Impulse Response) system. In FIG.
3D, a block diagram representing the transfer function Hw(z) of the Warburg impedance Wo is illustrated.

[0044] [Math. 21 Hw(z) = Einc,0 hkz-k ...(40)

[0045] A transfer function Hw(s) of the Warburg impedance Wo in the s region is represented by equation (41).

[0046] Hw(s) = Rwtanh(sTw)P/(sTw)P ...(41)

[0047] When the transfer function HL(s) is bilinear-transformed, the transfer function Hw(z) of the Warburg impedance Wo in the z region is represented by equation (42).

[0048] Hw(z) = Rwtanh[(2Tw/T)(1 - z-1)/(1 + z-1)1P
/{(2Tw/T)(1 - z-1)/(1 + z-1)1P ...(42)

[0049] Thus, from a comparison between the equations (40) and (42), it is found to be difficult to determine each of the coefficient hk in the FIR transfer function, respectively.
Therefore, the dependencies of Rw, Tw, and p on temperature 0 are determined according to the equation (41) based on the measurement results of Nyquist plots of the reference secondary battery at each of different temperatures 0 (see FIG. 4), respectively. Then, the equation (42) is subjected to inverse-FFT transform to be extracted as the coefficients of delay elements zk (k = 0 to n, where n is, for example, about several tens to 1000) in order to approximately define the transfer function Hw(z) of the Warburg impedance Wo as an FIR transfer function as in equation (40). This is derived from the fact that the influence of the Warburg impedance Wo is reflected on a low frequency side in the Nyquist plots. In other words, each of the coefficients hk that define the transfer function Hw(z) of the Warburg impedance Wo is defined as a dependent variable or a multivariable function Date recue /Date received 2021-11-24 when the temperature 0 and sampling frequency T are taken as main variables.

[0050] In FIG. 4, an example of Nyquist plots representing the measurement results of a complex impedance Z of the secondary battery 200 is illustrated together with an approximate curve of the plots. The horizontal axis is the real part ReZ of the complex impedance Z, and the vertical axis is the imaginary part -ImZ of the complex impedance Z. In a region of -ImZ > 0, lower frequency complex impedance Z is represented as ReZ
increases.

[0051] A value of ReZ when -ImZ = 0 (FIG. 4 (first evaluation section)) corresponds to the connection resistance component Ro of the secondary battery 200 (see FIG.
3A). A
section in a region of -ImZ < 0 (first evaluation section) surrounded by the dot-and-dash line in FIG. 4 corresponds to the impedance of wiring inductance Lo of the electrodes and the like of the secondary battery 200 (see FIG. 3B). A crushed semicircular shaped section in a region of -ImZ > 0 (second evaluation section) surrounded by the long dashed double-dotted line in FIG. 4 corresponds to reaction resistance and electric double layer (impedance of the first to the m-th RC parallel circuits) at the electrode interface of the secondary battery 200 (see FIG. 3C). The radius tends to be smaller as the temperature T
of the secondary battery 200 increases. The influence of the Warburg impedance Wo of the secondary battery 200 is reflected in an approximately linear section standing up at about 45 in a low frequency range in a region of ImZ > 0 (third evaluation section) surrounded by the dashed line in FIG. 4 (see FIG. 3D).

[0052] The approximate curve of the complex impedance Z of the secondary battery, which is represented by solid Nyquist plots in FIG. 4 is determined under the assumption that the transfer function H(t) of the equivalent circuit model of the internal resistance of the secondary battery is defined according to the equation (02). Thus, values of parameters Ro (see the equation (10)), Ri and Ci (see the equation (21)), Lo (see the equation (31)), Rw, Tw, and p (see the equation (41)) are determined at each temperature Date recue /Date received 2021-11-24 O. The value of the open circuit voltage OCV in each secondary battery model is identified by the measured value of the open circuit voltage OCV (see the equation (01)).
Then, secondary battery models are established by the parameter values for various types of secondary batteries 200.

[0053] (Secondary Battery Inspection Method) An inspection method of the secondary battery 200 executed by the secondary battery inspection device 100 having the configuration mentioned above will be described.

[0054] The impulse current I(t), the voltage V(t), and the temperature 0(t) of the secondary battery 200 are measured by a current sensor 51, a voltage sensor S2, and a temperature sensor SO, respectively, when the impulse current I(t) is applied by a charge/discharge device 300 to the secondary battery 200 to be inspected.

[0055] the measurement result of the temperature 0(t) of the secondary battery 200 is input to the temperature compensation element 110, and a temperature compensation model parameter according to the measurement result is output from the temperature compensation element 110. Specifically, values Ro(0), Ri(0), Ci(0), Lo(0), Rw(0), Tw(0), and p(0) of the parameters Ro (see the equation (10)), Ri and Ci (see the equation (20), Lo (see the equation (31)), and Rw and Tw (see the equation (41)) according to the temperature 0 are determined. These model parameters can be determined as average values of a good product population from mass-produced products of secondary batteries, and used as a reference model for pass/fail determination.

[0056] The temperature compensation model parameter is input from the temperature compensation element 110 to the first model parameter setting element 112, and the IIR
model parameters bo(0, bi(0, Ti), and ai(0, Ti) are determined by the first model parameter setting element 112 based on the temperature compensation model parameters Ri(0) and Ci(0) according to the first sampling period Ti (see the equations (221) to (223)).
The IIR model parameters bo(0, Ti), bi(0, Ti), and ai(0, Ti) are determined by the first Date recue /Date received 2021-11-24 model parameter setting element 112 based on the temperature compensation model parameter Lo(0) according to the first sampling period Ti (see the equations (321) to (323)). The FIR model parameter hk(0, Ti) is determined by the first model parameter setting element 112 based on the temperature compensation model parameters Rw(0, Ti), Tw(0, Ti), and p(0, Ti) according to the first sampling period Ti (see the equation (40)).

[0057] The voltage V(t) of the secondary battery 200 is inferred by the first voltage estimation element 114 based on the measurement result of the impulse current I(t) of the secondary battery 200 according to the secondary battery model defined by the transfer function H(t) according to the first sampling period Ti as a short period (for example, about 10 ms) (see the equation (01)). In FIG. 5A and FIG. 5B, the measured values of the voltage V of the secondary battery 200 at the time of discharge are illustrated by the dotted line, approximate curves representing the measured values of the OCV of the secondary battery 200 in each first sampling period Ti are illustrated by the dashed line, and approximate curves representing the estimation results of the voltage V(t) of the secondary battery 200 in each first sampling period Ti by the first voltage estimation element 114 are illustrated by the solid line, respectively. Since the open circuit voltage OCV is not considered in the secondary battery model, the estimation results D
of the voltage V(t) of the secondary battery 200 in each first sampling period Ti by the first voltage estimation element 114 is inferred based on the OCV (see FIG. 5A, FIG.
5B/down arrow D).

[0058] The temperature compensation model parameter is input from the temperature compensation element 110 to the second model parameter setting element 122, and the IIR model parameters bo(0, T2), b(0, T2), and a(0, T2) are determined by the second model parameter setting element 122 based on the temperature compensation model parameters R(0) and C(0) according to the second sampling period T2 (see the equations (221) to (223)). The IIR model parameters bo(0, T2), b(0, T2), and a(0, T2) are determined Date recue /Date received 2021-11-24 by the second model parameter setting element 122 based on the temperature compensation model parameter Lo(0) according to the second sampling period T2 (see the equations (321) to (323)). The FIR model parameter hk(0, T2) is determined by the second model parameter setting element 122 based on the temperature compensation model parameters Rw(0, T2), Tw(0, T2), and p(0, T2) according to the second sampling period T2 (see the equation (40)).

[0059] The voltage V(t) of the secondary battery 200 is inferred by the second voltage estimation element 124 based on the measurement result of the impulse current I(t) of the secondary battery 200 according to the secondary battery model defined by the transfer function H(t) according to the second sampling period T2 as a long period (for example, about 1 s) (see the equation (01)). In FIG. 5C, the measured values of the voltage V of the secondary battery 200 at the time of discharge are illustrated by the solid line, an approximate curve representing the measured values of the OCV of the secondary battery 200 in each second sampling period T2 is illustrated by the dashed line, and an approximate curve representing the estimation result of the voltage V(t) of the secondary battery 200 in each second sampling period T2 by the second voltage estimation element 124 is illustrated by the solid line. Since the open circuit voltage OCV is not considered in the secondary battery model, the estimation result E of the voltage V(t) of the secondary battery 200 by the second voltage estimation element 124 is inferred based on the OCV
(see FIG. 5C/down arrow E).

[0060] The voltage V(t) of the secondary battery 200 is input to the secondary battery inspection device 100, and the open circuit voltage OCV(t) of the secondary battery 200 is detected by the OCV detection element 102 based on input A concerned. Then, a difference C = A ¨ B of input A = V(t) and output B = OCV(t) of the OCV
detection element 102 is output by the subtraction element 104. The difference C is illustrated by the down arrow C in each of FIG. 5A, FIG. 5B, and FIG. 5C, which represents a Date recue /Date received 2021-11-24 difference between the measured value (solid line) of the voltage V of the secondary battery 200 at the time of discharge and the measured value dotted line) of the OCV.

[0061] The difference C is input from the subtraction element 104 to the division element 116, and the estimation result D of the voltage V(t) of the secondary battery 200 is input from the first voltage estimation element 114 to calculate a ratio C/D of both inputs.

[0062] C/D at each point of time in a first period (see FIG. 5A/region surrounded by the dashed box) immediately after the impulse current I(t) starts flowing from the division element 116 is input to the first evaluation element 142, and the connection resistance component Ro and the inductance element Lo of the secondary battery 200 in the first evaluation section is evaluated by the first evaluation element 142 based on a statistical index value, such as an average value of the input, a variance value, a deviation value, or an intermediate value of the maximum value and the minimum value. Here, since contribution by Lo is only the impedance on the imaginary axis and there is no contribution as the resistance value, the component to be evaluated is only Ro after all.
The closer C/D to 1, the smaller the change in the connection resistance component Ro of the secondary battery 200 is evaluated compared with the initial state or the good product population.

[0063] C/D at each point of time in a second period (see FIG. 5B/region surrounded by the dashed box) longer than the first period and starting at the elapse of the first period after the impulse current I(t) starts flowing from the division element 116 is input to the second evaluation element 144, and the reaction resistance and electric double layer (impedance of the first to the m-th RC parallel circuits) at the electrode interface of the secondary battery 200 in the second evaluation section are evaluated by the second evaluation element 144 based on the statistical index value of the input. The closer the C/D to 1, the smaller the change in the reaction resistance and electric double layer Date recue /Date received 2021-11-24 (impedance of the first to the m-th RC parallel circuits) at the electrode interface of the secondary battery 200 is evaluated compared with the initial state or the good product population. A tolerance level can be set to the calculated value of C/D for pass/fail determination.

[0064] The difference C is input from the subtraction element 104 to the division element 126, and the estimation result E of the voltage V(t) of the secondary battery 200 is input from the second voltage estimation element 124 to calculate a ratio of C/E of both inputs.

[0065] C/E at each point of time in a third period (see FIG. 5C/region surrounded by the dashed box) longer than the second period and starting at the elapse of the first period after the impulse current I(t) starts flowing from the division element 126 is input to the third evaluation element 146, and the Warburg impedance Wo of the secondary battery 200 in the third evaluation section is evaluated by the third evaluation element 146 based on the statistical index value of the input. The closer C/E to 1, the smaller the change in the Warburg impedance Wo of the secondary battery 200 is evaluated compared with the initial state or the good product population. A tolerance level can be set to the calculated value of C/E for pass/fail determination..

[0066] The evaluation results of the first evaluation element 142, the second evaluation element 144, and the third evaluation element 146 are output to an output interface wired or wirelessly connected to the secondary battery inspection device 100.

[0067] Each of the first evaluation element 142, the second evaluation element 144, and the third evaluation element 146 can make the determination with one measurement to estimate which component of the secondary battery is the cause of a failure depending on the combination of the determination results.
Advantageous Effects of Invention

[0068] According to the secondary battery inspection device 100 of the present Date recue /Date received 2021-11-24 invention and the secondary battery inspection method executed thereby, for example, as illustrated in Table 1, when the determination result of C/D related to the first evaluation section has a relation to a first determination reference value yl as expressed in equation (51), it is evaluated to be "OK (the resistance value of the cell constituent material is within a reference range)," while when the determination result of C/D does not have the relation expressed in the equation (51), it is evaluated to be "NG (the resistance value of the cell constituent material exceeds the reference)."

[0069] 1-y1 < C/D < 1+yl ...(51)

[0070] Further, as illustrated in Table 1, when the determination result of C/D related to the second evaluation section has a relation to a second determination reference value y2 as expressed in equation (52), it is evaluated to be "OK (there is no abnormality in reactivity between the positive electrode and the negative electrode)," while when the determination result of C/D does not have the relation expressed in the equation (52), it is evaluated to be "NG (there is abnormality in reactivity between the positive electrode and the negative electrode)."

[0071] 1-y2 < C/D < 1+y2 ... (52)

[0072] Further, as illustrated in Table 1, when the determination result of C/E related to the third evaluation section has a relation to a third determination reference value y3 as expressed in equation (53), it is evaluated to be "OK (there is no shortage of electrolyte, no deterioration of the electrolyte, or the like)," while when the determination result of C/E does not have the relation expressed in the equation (53), it is evaluated to be "NG
(there is a shortage of electrolyte, a deterioration of the electrolyte, or the like)."

[0073] 1-y3 < C/D < 1+y3 ...(53)

[0074] Thus, according to the present invention, not only can the pass/fail determination of the secondary battery be simply made but also it can be estimated which of components of the secondary battery causes a problem by one measurement.
Date recue /Date received 2021-11-24

[0075] The evaluation results may be transmitted from the secondary battery inspection device 100 to a client such as a smartphone, a tablet terminal, or a personal computer, and output to and displayed on an output interface (display) that constitutes part of the client.
Thus, since a defect factor can also be estimated while facilitating the inspection of the secondary battery 200, not only can the inspection accuracy be improved, but also a user of the client who engages in the production process can get smooth feedback.

[0076] [Table 11 Determination Determination Determination Result in First Result in Second Result in Third Individual Evaluation Evaluation Evaluation Abnormality Assumed Factor Section Section Section Content Determination Determination Determination Reference yl Reference y2 Reference y3 Increased Resistance of Cell Constituent Abnormality NG NG NG Material (Contact of Ro Failure or Electrical Resistance) Abnormality in Abnormali Reactivity of ty of Rn Cn OK NG NG Positive Electrode , and Negative Electrode Ion Diffusion Reaction in Abnormality OK OK NG Electrode, Such as of WO Shortage or Deterioration of Electrolyte Description of Reference Numerals

[0077] 100. secondary battery inspection device, 102...00V detection element (voltage recognition element), 104... subtraction element, 110.. .temperature compensation element, 112...first model parameter setting element, 114...first voltage estimation element, 122.. .second model parameter setting element, 124.. .second voltage estimation element, 200... secondary battery, 300...charge/discharge device.
Date recue /Date received 2021-11-24

Claims

- 17 -

1. A secondary battery inspection device comprising:
a voltage recognition element which recognizes a measurement result of voltage of a secondary battery when an impulse current flows into the secondary battery;
a model parameter setting element which identifies, based on a sampling period, a value of a model parameter of a secondary battery model in which impedance of internal resistance of the secondary battery is expressed by transfer functions respectively representing an IIR system and an FIR system;
a voltage estimation element which, when the impulse current is input to a specified model as the secondary battery model the value of the model parameter of which is identified by the model parameter setting element, estimates a model output voltage as a voltage change form output from the specified model; and an evaluation element which evaluates performance of the secondary battery according to the sampling period based on the measurement result of the voltage of the secondary battery recognized by the voltage recognition element, and the specified model output voltage estimated by the voltage estimation element.

2. The secondary battery inspection device according to claim 1, wherein the model parameter setting element individually identifies the value of the model parameter based on each of a plurality of sampling periods, respectively, the voltage estimation element estimates a plurality of model output voltages as voltage change forms respectively output from a plurality of specified models when the impulse current is input to the plurality of specified models as individual secondary battery models with the values of the model parameter identified by the model parameter setting element, and the evaluation element evaluates a plurality of performances of the secondary battery respectively according to respective of the plurality of sampling periods based on the measurement result of the voltage of the secondary battery recognized by the voltage recognition element, and respective of the plurality of specified model output voltages estimated by the voltage estimation element.

3. The secondary battery inspection device according to claim 1 or 2, further comprising a temperature compensation element which recognizes a measurement result of temperature of the secondary battery, wherein the model parameter setting element corrects the value of the model parameter based on the measurement result of the temperature of the secondary battery recognized by the temperature compensation element.

4. A secondary battery inspection method comprising:
a voltage recognition process of recognizing a measurement result of voltage of a secondary battery when an impulse current flows into the secondary battery;
a model parameter setting process of identifying, based on a sampling period, a value of a model parameter of a secondary battery model in which impedance of internal resistance of the secondary battery is expressed by transfer functions respectively representing an IIR system and an FIR system;
a voltage estimation process in which, when the impulse current is input to a specified model as the secondary battery model the value of the model parameter of which is identified in the model parameter setting process, a model output voltage as a voltage change form output from the specified model is estimated; and an evaluation process of evaluating performance of the secondary battery according to the sampling period based on the measurement result of the voltage of the secondary battery recognized in the voltage recognition process, and the specified model output voltage estimated in the voltage estimation process.